Optimum Strategies for Using Adobe Photoshop CS2 in Scientific and Medical Imaging
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WHITE PAPER Optimum Strategies for Using Adobe Photoshop CS2 in Scientific and Medical Imaging The needs of the scientific and medical communities with respect to working with digital images are much the same as in any other profession—quality, precision, power, TABLE OF CONTENTS and performance. But in addition to these requirements, scientists and researchers 2 Overview of Photoshop CS2 require security, clarity, and accurate records. 5 The Scientific Imaging Workflow Scientific images come from a variety of sources, including microscopic and 5 Capturing, Organizing, and radiological devices, computerized scanning equipment (CAT, PET, MRI), and Converting Images in Adobe Bridge specialized camera equipment. The images can be in a variety of formats, and can range 6 Image Enhancement from monochromatic to 32‑bit high dynamic range (HDR) color. Researchers and 9 Image Analysis practitioners must be able to view and eke out the maximum detail and resolution from 10 Collaboration and Output these images without altering image data. They need to be able to organize thousands of often similar images, maintain and view metadata contained within the images, and apply labels and record metadata. They require efficient methods to share their results with colleagues for analysis and presentations, and that their results come from precise, nondestructive image manipulation tools with efficient, automatic procedure records for both audit trail and publication. Adobe® Photoshop® is the industry standard in digital imaging. Photoshop includes all of the tools necessary to facilitate the efficient capture, manipulation, enhance‑ ment, organization, and sharing of scientific and medical images. Many dedicated, discipline‑specific software packages are capable of fine quantitative analysis, but their high cost and difficulty of use limits their applicability in many contexts. Similarly, equipment and lenses capable of the highest precision image capture exist, but their cost limits their availability to many researchers and departments. In contrast, Adobe Photoshop CS2 is an affordable, easy‑to‑use, comprehensive solution that is capable of handling the vast majority of native image formats. Its powerful tools overcome the limitations of conventional hardware and assist in the performance of high quality, first approximation qualitative analysis. Photoshop CS2 offers a complete end‑to‑end workflow that starts with the image capture device and ends with final images in the widest variety of output options. In addition, a wide variety of third‑ party plug‑ins are available to enhance the capabilities of the program, many designed specifically for scientific use. Adobe also makes available the Adobe Studio Exchange at http://share.studio.adobe.com, where users can share and exchange scripts that further enhance the capabilities of Photoshop. The extensive scripting and automation support in Photoshop also greatly facilitates the batch processing of multiple images, which can provide increased efficiency in scientific and technical workflows involving large numbers of images. This white paper details the Photoshop CS2 features of particular interest to the scientific and medical communities, as well as describing some typical scientific and medical digital imaging workflows. Overview of Photoshop CS2 Before working with Photoshop CS2, it is helpful to become familiar with some of the terminology and concepts. Multilayered image files A file in Photoshop consists of a series of image layers stacked one on top of the other. Generally, a new image opened in Photoshop contains one layer. By adding new layers for notes, labels, and image adjustments, you can preserve the original image on a single layer. Using multiple layers lets you reveal the original nonenhanced image at any time, and easily reverse any changes you make by simply deleting the layers containing the changes. Layers also facilitate composites and montages, since each image or segment can reside on its own layer. Nondestructive adjustment layers An adjustment layer is a special layer that contains a filter or effect that is applied to the layers beneath it. Adjustment layers are nondestructive, because they are separate from the data itself. They can be modified, added to, or removed with no permanent effect to the original image data. The multilayered Photoshop file format allows you to isolate labels, callouts, and enhancements from the image data, which is preserved on the original locked background layer. Multiple format compatibility Photoshop CS2 can read a wide variety of image formats, including Photoshop PSD and PSB, GIF, JPEG, EPS, PICT, Pixar, PNG, Portable Bit Map, Scitext CT, Targa, TIFF, Cineon, PCX, BMP, Radiance, Wireless Bitmap, DNG, and most Camera Raw formats, such as CRW and NEF. You can also add more specialized image format support with plug‑ins, many of which can be located by searching the partners database at adobe.com. Multiple format support makes it easier to handle varied source data from scientific devices and specialized cameras. Color depth and pixel resolution The vast majority of Photoshop features are now available for 16‑bit color images, and Photoshop CS2 introduces 32‑bit, floating‑point, HDR capabilities. Combined with a maxi‑ mum image size of 300,000 x 300,000 pixels and the newer PSB Large Document Format, Photoshop CS2 is capable of handling the most complex images, including those obtained by high‑resolution medical and satellite devices and cameras. When creating composite images, either manually or using the Photomerge® feature to stitch tiled images together, the maximum pixel dimensions of a Photoshop CS2 file enable the compositing of up to 900 transmission elec‑ tron microscopy (TEM) negatives into one image. The image size is now limited predominantly by the capabilities of computer hardware. Optimum Strategies for Using Adobe Photoshop CS2 2 in Scientific and Medical Imaging Qualitative analysis by selection and measurement Photoshop CS2 has a variety of precise methods to select parts of images, including tools like the Magic Wand and Magnetic Lasso. Combining area selection with the Measure tool, Histogram palette, and Info palette enables you to perform qualitative image analysis and comparison. For example, you can compare before and after slides to determine if a tumor is shrinking. You can also easily compare two images visually using the Matched Zoom and Matched Scrolling features. With these enabled, the same area of each image is displayed at the same magnification. If one image is moved or its magnification changed, the same changes automatically occur in the other open images. Text and vector tools for labeling and demonstration The text and vector shape tools let you create and preserve live, editable type and shape layers in any image. You can use these tools to label image features quickly and easily without affecting the image data. You can keep text and vector shape layers separate and hidden, so you can use the same images in all contexts. Maintaining image integrity When enhancing scientific images, care must be taken to avoid modifications that can affect the researcher’s or practitioner’s conclusions. For this reason, it is always best to restrict image enhancement to those filters and adjustments that affect the entire image at once, and do not affect the visual relationships between objects in the images. Best practice is therefore to make adjustments to the image as a whole rather than to selected areas of the image. Photoshop CS2 provides filters and image adjustments, such as Levels, Color Balance, Smart Sharpen, and Match Color, which enhance the ability to discern detail in scientific images and, thereby, enhance image analysis rather than skewing its results. When images are used for demonstration rather than analysis, such alterations are acceptable for purposes of clarity, so retouching tools, like the Spot Healing Brush, can make images more useful. For example, an educator might want to show one particular cell structure to a class. The Spot Healing Brush can be used to remove other visible features of the image, leaving only the cell or structure of interest. Collaboration with Adobe PDF Conveying information about images to colleagues elsewhere can be extremely difficult, espe‑ cially when you are dealing with highly detailed images in proprietary formats. Photoshop CS2 provides two simple but powerful resources to facilitate collaboration. The Notes tool lets you attach virtual sticky notes to an image, and the Audio Annotation tool lets you embed voice annotation inside the image file. Both text and audio annotations are carried with the image when it is exported to an Adobe PDF file. You can e‑mail the PDF file to a colleague, who can view the image and notes, and listen to any audio annotations using the free and easily available Adobe Reader®. If the recipients have Adobe Acrobat®, they can also add their own comments to the PDF document and return it to the originator for ongoing collaboration. Where security is a concern, Photoshop CS2 includes settings to restrict whether and in which way readers can open, print, or change the PDF document. The Notes tool allows you to easily attach notes to any image. If the file is saved to an Adobe PDF file, the notes become comments in Adobe Acrobat or Adobe Reader. Optimum Strategies for Using Adobe Photoshop CS2 3 in Scientific and Medical Imaging Image organization and management Specialists dealing with digital images must also deal with the proliferation of those images and managing them. They must be able to locate previous images quickly and compare them to more recent ones, or they need to collect them for presentation or publication. In addition, the details about the images must be as accessible as the images themselves. Photoshop CS2 now includes Adobe Bridge for file management, and its many features are ideal solutions to the challenges of scientific imaging. Formerly included within Photoshop as the File Browser, Bridge offers multiple views and scalable image thumbnails for simple image browsing and detailed preview‑ ing.